As technology developed, optoelectronic semiconductor devices have contributed a lot to energy transmission and conversion. For example, optoelectronic semiconductor devices can be used in system operation such as optical fiber communication system, optical storage system, and military system. According to the energy conversion mode, optoelectronic semiconductor devices can be classified as three categories: conversion from electrical power to light such as light-emitting diode and laser diode; conversion from light to electrical signal such as optical detector; and conversion from light into electrical power such as solar cell.
Growth substrate is important for forming an optoelectronic semiconductor device. Semiconductor epitaxial structure of the optoelectronic semiconductor device is formed on and supported by the growth substrate. Therefore, the quality of the optoelectronic semiconductor device is determined by a suitable growth substrate.
However, a suitable growth substrate sometimes is not suited to be a support substrate for the optoelectronic semiconductor device. For example, in order to obtain a high-quality semiconductor epitaxial structure for a light-emitting diode that can emit red light, the opaque GaAs substrate is usually preferred as the growth substrate for its lattice constant is the most close to that of the semiconductor epitaxial structure for red light-emitting diode. But, as the light-emitting diode is used for emitting light, the opaque growth substrate blocks the light and therefore decreases the light-emitting efficiency of the light-emitting diode in operation.
In order to satisfy the different conditions of the growth substrate and the support substrate required for different optoelectronic semiconductor devices, the technique of transferring substrate is developed. To be more specific, the semiconductor epitaxial structure is firstly formed on the growth substrate and then the semiconductor epitaxial structure is transferred to the support substrate. After the support substrate is bonded with the semiconductor epitaxial structure, the removal of the growth substrate is the key technique in the process of substrate transfer.
The method of removing the growth substrate mainly comprises dissolving method such as wet etching, physical method such as polishing and cutting, or the method of forming a sacrificial layer between the semiconductor epitaxial structure and the growth substrate in advance and then removing the sacrificial layer by etching. However, both of the wet etching method and the physical method such as polishing and cutting, damage the growth substrate. Furthermore, considering the importance of the environmental protection and the energy conservation, it is wasteful if the growth substrate cannot be reused.